1. Field of the Invention
The present invention relates to voltage controlled oscillators (VCOs) and, particularly, to such oscillators implemented on integrated circuits (ICs).
2. Description of the Prior Art
VCOs implemented on ICS are known. See, for example, U.S. Pat. No. 5,973,575, “Fully Monolithic Voltage Controlled Oscillator with Wide Tuning Range,” Kamogawa et al, filed Feb. 12, 1998, issued Oct. 26, 1999, which is incorporated in its entirety herein by reference.
IC-implemented voltage controlled oscillators often experience undesirable noise (e.g., phase noise) from sources, among others, such as the supply voltage or source of potential Vcc. See, for example, the chapter entitled “How Phase Noise Appears in Oscillators” of the book Analog Circuit Design-RF Analog-to-Digital Converters; Sensor and Actuator Interfaces; Low-Noise Oscillators; PLLs and Synthesizers, published by Kluwer Academic Publishers, Boston, November 1977, ISBN 0-7923-9968-4; and also “Concepts and Methods in Optimization of Integrated LC VCOs”, IEEE Journal of Solid-State Circuits, Vol. 36, No. 6, June 2001, pgs. 896-909, by Ham and Hajimiri. The sources of phase noise in a VCO need not be further discussed.